Suspension grid ceilings are widely used commercially and industrially. Such grid suspension ceilings typically include a plurality of horizontally flanged runners placed at 90.degree. angles and suspended across a ceiling area so as to form square or rectangular grids in which ceiling panels are placed. With the advent of high technology industries, such as, for example, electronics, optics, telecommunications, robotics, medicine, and biotechnology, there is a need for such ceiling constructions which introduce a minimum of particles into the room. Such commercial and industrial environments are commonly referred to as clean rooms.
The conventional ceiling panels used in clean room construction are typically made of mineral fiber, fiberglass, gypsum or the like. These panels have a front surface disposed downwardly when the panel is placed in the suspension grid. The front surface is either smooth, or it may be perforated and/or contoured for sound absorption as in conventional acoustical ceiling panels. The front surface exposed to the interior of the room, as well as the reverse surface, when used in clean room systems, are typically sealed with a laminated facing of latex, aluminum or the like, to inhibit the release of particles from the ceiling panel into the clean room environment. Such surfacing is relatively effective in preventing the escape of particles from the exposed front surface of the ceiling panel to the clean room environment. However, a persistent problem heretofore has been the elimination of particles which escape from the edge of the ceiling panels, and/or the escape of particles from the space above the suspended ceiling into the clean room between the ceiling panel and the runners or horizontal flanges on which they are supported.
Various attempts have been made to prevent the introduction of particles into the clean room from or across the edges of the ceiling panels in the grid suspension system. Some relatively simple attempts have included sealing the ceiling panel edges and the use of a gasket material between the suspension grid horizontal flanges and the periphery of the front face of the ceiling panel. For example, it is known to seal the exposed edge surfaces of the ceiling panel with latex or a hard case adhesive. This has not been particularly effective because the edges of the ceiling panels are subject to damage by rubbing and/or bumping against the vertical portion of the runners in the ceiling grid suspension, particularly during installation and maintenance, and the edge sealant material tends to penetrate into the ceiling panel and make the edges brittle and flaky, particularly in the case of the hard case adhesives, thereby contributing to the generation of particles which escape into the clean room environment. A flexible tape has also been used to seal the edges of the ceiling panels, and while this has been relatively effective in inhibiting particle generation, it has been labor intensive as the edge of each ceiling panel must be taped manually prior to installation. This has significantly increased the cost and time of the installation.
Similarly, it has been known to use a foam adhesive tape to form a gasket or sealing surface between the ceiling panel and the horizontal flanges in the grid suspension system. Again, however, this installation is labor intensive in that the tape is applied manually to each horizontal flange and/or each ceiling panel at the installation site. An alternative to this has recently been the introduction of T-bar grid suspension runners, typically of aluminum, in which a channel is formed in the horizontal flange for placing the foam tape in the channel on the horizontal flange during manufacture thereof. However, this type of grid suspension system has been expensive because of the high cost associated with manufacturing the runners with the required profile, i.e. with the channel formed in the horizontal flange thereof. Moreover, this approach still does not address the need to seal the edge of each ceiling panel.
A more elaborate approach to preventing particle generation from and transmission through the grid suspension ceiling has been the use of runners in which a relatively deep channel is formed in the upward face of the horizontal flanges thereof. This type of grid system is typically suspended above the room, and then the channels in the horizontal flanges are filled with a jelly material which is heated and poured in a relatively liquid state into the channels of the runners. When the sealing liquid cools, it viscosifies and gels in the channels. This system is then used in conjunction with ceiling panels which are manufactured with an L-shaped flanged inserted into each edge of the ceiling panel. The L-shaped flange protruding from the ceiling panel is inserted into the jelly in the channel of each runner to suspend the ceiling panel in the grid system while forming a seal through immersion of the L-shaped flange of the ceiling panel into the jelly placed in the channel of the horizontal flanges on the grid suspension system.
In Jordan, Jr., et al. U.S. Pat. No. 3,084,402 there is described an acoustical panel with which tape and gaskets are used around the edge of the ceiling panel to prevent air and sound leakage past the edges of the panel.
In Soltis U.S. Pat. No. 4,603,618, there is described an air filtering distribution system in which filter membrane panels are suspended below the grid suspension ceiling system.
In Olson U.S. Pat. No. 3,325,954, there is described a ventilating ceiling system which employs various gaskets and other resilient sealing means at the periphery of the ceiling panel.
In Wilson U.S. Pat. No. 3,460,299, there is described a luminous sound absorbing ceiling which employs dual, parallel plastic films stretched across upper and lower surfaces of peripheral frames.
Various lighting fixture installations and grid suspension ceilings are described in Blum U.S. Pat. No. 4,272,804; Shorette U.S. Pat. No. 4,075,775; and Sutter U.S. Pat. No. 3,555,267.
Glass panes having profiled edges are described in Ohlenforst, et al. U.S. Pat. No. 4,775,570 and Kunert U.S. Pat. No. 4,477,507.